Doctor of the Church (Latindoctor, teacher, from Latin docere, to teach) is a title given by a variety of Christian churches to individuals whom they recognize as having been of particular importance, particularly regarding their contribution to theology or doctrine.

In the Western church four eminent Fathers of the Church attained this honour in the early Middle Ages: Saint Gregory the Great, Saint Ambrose, Saint Augustine, and Saint Jerome. The "four Doctors" became a commonplace among the Scholastics, and a decree of Boniface VIII (1298) ordering their feasts to be kept as doubles in the whole Church is contained in his sixth book of Decretals (cap. "Gloriosus", de relique. et vener. sanctorum, in Sexto, III, 22).[1]

In the Eastern Church three Doctors were pre-eminent: Saint John Chrysostom, Saint Basil the Great, and Saint Gregory Nazianzen. The feasts of these three saints were made obligatory throughout the Eastern Empire by Leo VI the Wise. A common feast was later instituted in their honour on 30 January, called "the feast of the three Hierarchs". In the Menaea for that day it is related that the three Doctors appeared in a dream to John Mauropous, Bishop of Euchaitae, and commanded him to institute a festival in their honour, in order to put a stop to the rivalries of their votaries and panegyrists. This was under Alexius Comnenus (1081-1118; see "Acta SS.", 14 June, under St. Basil, c. xxxviii). But sermons for the feast are attributed in manuscripts to Cosmas Vestitor, who flourished in the tenth century. The three are as common in Eastern art as the four are in Western. Durandus (i, 3) remarks that Doctors should be represented with books in their hands. In the West analogy led to the veneration of four Eastern Doctors, Saint Athanasius being added to the three hierarchs.[1]

To these great names others have subsequently been added. The requisite conditions are enumerated as three: eminens doctrina, insignis vitae sanctitas, Ecclesiae declaratio (i.e. eminent learning, a high degree of sanctity, and proclamation by the Church). Benedict XIV explains the third as a declaration by the supreme pontiff or by a general council. But though general councils have acclaimed the writings of certain Doctors, no council has actually conferred the title of Doctor of the Church. The procedure involves extending to the universal church the use of the Divine Office and Mass of the saint in which the title of doctor is applied to him. The decree is issued by the Congregation for the Canonizations and approved by the pope, after a careful examination, if necessary, of the saint's writings. It is not in any way an ex cathedra decision, nor does it even amount to a declaration that no error is to be found in the teaching of the Doctor. It is, indeed, well known that the very greatest of them are not wholly immune from error. No martyr has ever been included in the list, since the Office and the Mass are for Confessors. Hence, as Benedict XIV points out, Saint Ignatius of Antioch, Saint Irenaeus, and Saint Cyprian are not called Doctors of the Church.

Traditionally, in the Liturgy, the Office of Doctors was distinguished from that of Confessors by two changes: the Gospel reading Vos estis sal terrae ("You are the salt of the earth"), Matthew 5:13–19, and the eighth Respond at Matins, from Ecclesiasticus 15:5, In medio Ecclesiae aperuit os ejus, * Et implevit eum Deus spiritu sapientiae et intellectus. * Jucunditatem et exsultationem thesaurizavit super eum. ("In the midst of the Church he opened his mouth, * And God filled him with the spirit of wisdom and understanding. * He heaped upon him a treasure of joy and gladness.") The Nicene Creed was also recited at Mass, which is normally not said except on Sundays and the highest-ranking feast days. The 1962 revisions to the Missal dropped the Creed from feasts of Doctors.

As of 2015[update], the Catholic Church has named 36 Doctors of the Church. Of these, the 17 who died before the Great Schism of 1054 (marked * in the list below) are also venerated by the Eastern Orthodox Church (Gregory of Narek was from the Armenian Apostolic Church which was not in communion with Chalcedonian Church). Among these 36 are 27 from the West and 9 from the East; 4 women; 18 bishops, 12 priests, 1 deacon, 3 nuns, 1 consecrated virgin; 26 from Europe, 3 from Africa, 7 from Asia. More Doctors (12) lived during the 4th century than any other; eminent Christian writers of the 1st, 2nd and 3rd centuries are usually referred to as the Apostolic Fathers or Ante-Nicene Fathers, while the 9th, and 20th centuries have so far produced no Doctors at all. The shortest period between death and nomination was that of Alphonsus Liguori, who died in 1787 and was named a Doctor of the Church in 1871 - a period of 84 years; the longest was that of Ephrem the Syrian, which took fifteen and a half centuries.

On 20 August 2011, Pope Benedict XVI announced that he would soon declare St. John of Ávila a Doctor of the Church.[3] Although no official announcement was given, it was reported in December 2011 that Pope Benedict intended to declare Hildegard of Bingen as a Doctor of the Church despite her not yet having been officially canonised.[4] The liturgical cult of St. Hildegard of Bingen was officially extended to the universal Church by Pope Benedict XVI on 10 May 2012, clearing the way for her to be named a Doctor of the Church.[5] Pope Benedict formally declared SS John of Ávila and Hildegard of Bingen to be Doctors of the Church on 7 October 2012.[6]

Though not named Doctors of the Church or even canonized, many of the more celebrated doctors of theology and law of the Middle Ages were given an epithet which expressed the nature of their expertise. Among these are Bl.John Duns Scotus, Doctor subtilis (Subtle Doctor); Bl.Ramon Llull, Doctor illuminatus (Illuminated Doctor); Bl.John of Ruysbroeck, Doctor divinus ecstaticus (Ecstatic Doctor); Alexander of Hales, Doctor irrefragabilis (Unanswerable Doctor); Roger Bacon, "Doctor Mirabilis" (Wondrous Doctor); Gregory of Rimini, Doctor authenticus (Authentic Doctor); John Gerson, Doctor christianissimus (Most Christian Doctor); Nicholas of Cusa, Doctor christianus (Christian Doctor); and the priest and professor Francisco Suárez, Doctor eximius (Exceptional Doctor).

The churches of the Anglican Communion tend not to use the term "Doctor of the Church" in their calendars of saints, preferring expressions such as "Teacher of the Faith". Those thus recognized include figures from before and after the Reformation, most of whom are also recognized as Doctors of the Church in the Latin rite of the Catholic Church. Those designated as Teachers of the Faith in the Church of England's calendar of saints are as follows:

Since all of the above appear in the calendar at the level of Lesser Festival or Commemoration, their celebration is optional. Similarly, because "In the Calendar of the Saints, diocesan and other local provision may be made to supplement the national Calendar",[9] those Doctors of the Church recognized by the Catholic Church may also be celebrated in the Church of England.